This study will determine the effects of ultrasound on the formation of specific neuronal connections, a process that is essential for the normal functioning of the nervous system. During normal development, many phenomena including neuronal migration, differentiation, and axon outgrowth make important contributions to the final pattern of nerve cell innervations. The proposed research will investigate the effect of ultrasound on three critical developmental processes: 1) the migration of neural crest cells, 2) the projection pattern and timing of axonal growth, 3) specific synapse formation. The model system used in these investigations will be the sympathetic nervous system of the chick. The sympathetic system is especially suited to this study as it provides a less complex system compared with the central nervous system and extensive developmental studies have already been done. The chick embryo was chosen for obvious advantages: 1) The "in ovo" embryo, being an independent system is not influenced by the condition of a maternal host and, therefore, reacts directly to teratogenic agents; 2) The sympathetic system of the chick is similar to that of the mammal; and 3) Quail cells can be used as natural markers to study neural crest migration. The techniques that will be used are extremely sensitive and will readily detect any teratogenic effects of ultrasound. Using a quail-chick transplanation technique, the migration pattern of neural crest cells will be determined. Utilization of a horseradish peroxidase (HRP) axonal tracing technique allows the timing and projection patterns of axonal outgrowth to be precisely identified. In addition, intracellular recording techniques will be used to determine the pattern of specific ganglion cell innervation.